When the Author server restarts, it can look, to the users, like it is hanging because as soon as they click on a node in the left hand nav tree they see "Loading" in the central pane. It just sits there saying "Loading" for a long, long, long time.

This can be caused by having lots of old Workflow instances hanging around (check /etc/workflow/instances). In which case, you should ensure that you install the Workflow purge tool from Adobe.

The purge tool by default will clear out any Workflow instances which are less than 14 days old (well the version I have says > 1 day but the code was actually > 14 days). It can be configured to only purge COMPELTED workflow, or ALL of them. However, beware that the default configuration (in my version 1.6.1 anyway) will only purge the following workflow models :-